1. Technical Field
This invention relates to an inflating-type safety system for motor vehicles, and more particularly to a multistage-inflating hybrid inflator capable of inflating an air bag rapidly and reducing noxious gas contained in combustion gas, and an air bag system using the same inflator.
The present invention also relates to a retainer for a gas generator, a gas generator using the same retainer, a hybrid inflator using the same gas generator, and an air bag system using the same hybrid inflator.
Furthermore, the present invention relates to a multistage-inflating hybrid inflator having ignition means in which a single initiator collar and two initiators are formed as a single member, and to an air bag system using the same hybrid inflator.
2. Description of the Prior Art
With the development of an inflator for an inflating-type safety system for motor vehicles, a hybrid inflator using both a pressurized gas and a solid gas generating agent is attracting attention. A main design requirement for a hybrid inflator is that the inflator inflates an air bag by a predetermined amount in a predetermined time so that the air bag is effectively activated. Various proposals concerning a structure to meet the requirement have heretofore been made (for example, as referred in JP-A 8-282427). Since such a hybrid inflator is designed to be installed in a motor vehicle, the weight and dimensions of the inflator, which have influence upon the weight of the motor vehicle, constitute an important design requirement therefore. Furthermore, designing an inflator capable of being manufactured easily, not having a possibility of gas leakage, and capable of reducing a noxious gas contained in a combustion gas to a low level is demanded.
U.S. Pat. No. 3,773,353 and U.S. Pat. No. 3,868,124 disclose inflators provided with two gas generating chambers. In both of these inflators, the pressures in the two gas generating chambers are at normal levels prior to actuation of the inflators, and oxygen gas is not contained in the inflators. Therefore, before putting these inflators into practical use, they have to be improved with respect to many points, i.e., a stable combustion of a gas has to be secured and the safety of a combustion gas have to be attained.
U.S. Pat. No. 5,351,988 discloses a hybrid inflator including two gas generating chambers, one of the gas generating chambers being disposed outside of an inflator housing, and pressure in the one gas generating chambers is kept at a normal level.
As a hybrid inflator, there is a single type inflator having one gas generating chamber and a dual type inflator having two gas generating chambers. The single type inflator uses a retainer for adjusting an amount of gas generating agents, and the dual type inflator uses a retainer for adjusting the dosage and for separating the two gas generating chambers from each other.
As described above, the retainer is required to have the dosage-adjusting function and the separating function of the two gas generating chambers. Especially in the case of the dual type hybrid inflator, the separating function of the two gas generating chambers is essential. In other words, when a first gas generating agent in a first gas generating chamber burns, it is important to completely eliminate a possibility such that high temperature combustion gas flows into a second gas generating chamber to burn a second gas generating agent in order to normally activate the hybrid inflator. Further, in addition to this function, it is important that the mounting operation of the retainer is simple in the industrial aspect.
An object of the present invention is to provide a multistage-inflating hybrid inflator capable of inflating an air bag rapidly, and reducing noxious gas contained in combustion gas without a weight increase of the inflator; and an air bag system using the hybrid inflator.
As described above, another object of the present invention is to provide a retainer for a gas generator in which, when it is used as a retainer for a gas generator of a hybrid inflator for example, the retainer has functions to adjust an amount of the gas generating agents and to separate the gas generating chambers, and the operation of mounting the retainer to the gas generator is facilitated.
Still another object of the present invention is to provide a gas generator using the retainer, a hybrid inflator using the gas generator, and an air bag system using the hybrid inflator.
Further another object of the present invention is to provide a multistage-inflating hybrid inflator comprising ignition means in which a single initiator collar and two initiators are fixed to be a single member, and an air bag system using the hybrid inflator.
The present invention provides a multistage-inflating hybrid inflator for a safety system of vehicles provided with an air bag, which comprises an inflator housing, a gas generator installed in the inflator housing, and an ignition means chamber joined to the gas generator, wherein the interior of the inflator housing is filled with a pressurized medium containing an inert gas, the gas generator having first and second gas generating chambers including their respective gas generating means.
Further, the present invention provides a multistage-inflating hybrid inflator for a safety system of vehicle provided with an air bag, which comprises an inflator housing, a gas generator installed in the inflator housing, and an ignition means chamber connected to the gas generator, the interior of the inflator housing being filled with a pressurized medium containing an inert gas, the gas generator having a first gas generating chamber and a second gas generating chamber storing a gas generating means, respectively, the hybrid inflator further comprising a principal closing means to close, before actuation, a flow of the pressurized medium outward to discharging port, and rupturing means for rupturing the principal closing means upon actuation, and the rupturing means actuating with increase of the internal pressure of the housing or by electric means.
In the multistage-inflating hybrid inflator of the present invention, an arrangement of the first gas generating chamber and the second gas generating chamber can appropriately be set. For example, the gas generating chambers may be arranged in series and adjacently to each other in the longitudinal direction of the inflator housing, the gas generating chambers may be arranged in series, facing each other, in the longitudinal direction of the housing, or the gas generating chambers may be aligned in parallel to each other in the lateral direction of the housing and are adjacent to or separate from each other. Among the above arrangements, the one in which the gas generating chambers are arranged in series and adjacently to each other in the longitudinal direction of the inflator housing is preferable.
In the multistage-inflating hybrid inflator of the present invention, the principal closing means for blocking a flow of the pressurized medium is provided in a gas flowpath, leading to the discharging port, of the pressurized medium of the hybrid inflator at a desired position so that the pressurized medium charged in the inflator housing may not leak before actuation. Upon actuation, the rupturing means for rupturing the principal closing means to obtain the gas flowpath is required. The rupturing means is not especially limited to a certain structure as long as the flowpath can be ensured. In the present invention, the rupturing means actuates with increase of the internal pressure of the housing or by electric means.
The rupturing means actuating with increase of the internal pressure of the inflator housing ruptures the principal closing means only by increase of the internal pressure caused by high temperature gas generated upon combustion of the gas generating means in the gas generating chamber. As the rupturing means actuated by electric means, for example, means such that the principal closing means is ruptured by actuating an electric type igniter which is disposed in the vicinity of the principal closing means, preferably disposed to face closer to the principal closing means. At that time, a booster can be used in combination if required. In either of the two rupturing means, size, strength and the like of the principal closing means are determined in view of the size, strength and the like of the principal closing means so as to reliably rupture the principal closing means to obtain the flowpath of the pressurized medium.
Further, the present invention provides a multistage-inflating hybrid inflator for a safety system of vehicle provided with an air bag, comprising an inflator housing, a gas generator installed in the inflator housing, and an igniting means chamber connected with the gas generator, the inflator housing being charged with a pressurized medium including an inert gas, the gas generator comprising a first gas generating chamber and a second gas generating chamber, each including gas generating means, the inflator further comprising principal closing means to close, before actuation, transition of the pressurized gas outward to discharging ports and a projectile to rupture the principal closing means upon actuation
In the multistage-inflating hybrid inflator of the present invention, an arrangement of the first gas generating chamber and the second gas generating chamber can be set appropriately. For example, the gas generating chambers may be arranged in series and adjacently to each other in the longitudinal direction of the inflator housing, the gas generating chambers may be arranged in series, faced to each other, in the longitudinal direction of the housing, or the gas generating chambers may be aligned in parallel to each other in the lateral direction of the housing and adjacent to or separate from each other. Among the above arrangements, the one in which the gas generating chambers are arranged in series and adjacently to each other in the longitudinal direction of the inflator housing is preferable.
In the present invention, a top end of a projectile which utilizes a pressure for rupturing the principal closing means upon actuation can be disposed in the same space as a space, inside the housing, where the pressurized medium is charged.
In such a multistage-inflating hybrid inflator, the principal closing means for blocking a flow of the pressurized medium is provided in the gas flowpath, leading to the discharging port, of the pressurized medium of the hybrid inflator at a desired position so that the pressurized medium charged in the inflator housing may not leak before actuation. As the rupturing means for rupturing the principal closing means to ensure the gas flowpath upon actuation, a projectile which utilizes pressure, i.e. rupturing means such that a projectile collides against the principal closing means, can be used. The top end of the projectile is disposed in the same space as the space, inside the inflator housing, where the pressurized medium is charged. Size, strength, weight and the like of the projectile are determined in view of the size, strength and the like of the principal closing means so as to reliably rupture the principal closing means to ensure the flowpath of the pressurized medium. A guiding member for conducting the projectile to the principal closing means can be provided in order to reliably smash the principal closing means.
Further in the present invention, the top end of the projectile which utilizes pressure for rupturing the principal closing means upon actuation can be disposed in a space other than the space, inside the inflator housing, where the pressurized medium is charged.
In such a multistage-inflating hybrid inflator, the principal closing means for closing a flow of the pressurized medium is provided in the gas flowpath, leading to the discharging port, of the pressurized medium of the hybrid inflator at a desired portion so that the pressurized medium filled in the inflator housing does not leak before actuation. As the rupturing means for rupturing the principal closing means to ensure the gas flowpath upon actuation, a projectile which utilizes pressure, i.e. a rupturing means such that a projectile collides against the principal closing means, can be used. The top end of the projectile is disposed in a space (referred to as xe2x80x9ca small spacexe2x80x9d here and naturally, a relation of volume of xe2x80x9clarge space greater than small spacexe2x80x9d is established) other than the space (excluding the space where the gas generator and the igniting means chamber are provided. Here, the space is referred as xe2x80x9ca large spacexe2x80x9d), in the inflator housing, where the pressurized medium is charged. The small space can be formed with a cylindrical member for example, and the large space and the small space communicate with each other only through a predetermined number of small holes (gas-flow holes) Size, strength, weight and the like of the projectile are determined in view of the size, strength and the like of the principal closing means so as to reliably rupture the principal closing means to ensure the flowpath of the pressurized medium.
The retainer for a gas generator of the present invention is suitable for a gas generator of a hybrid inflator, and is applicable to a single type inflator having one gas generating chamber, a dual type inflator having two gas generating chambers, and an inflator having more than three gas generating chambers.
The present invention provides a retainer for a gas generator disposed in the gas generator having one or more gas generating chambers, wherein the retainer is made of a cylindrical member having one end closed and the other end open.
Side walls of the retainer for a gas generator may have a constant length or different lengths in part. Or one side wall of the retainer may be longer than the side wall being opposite thereto. By appropriately adjusting the length of the side walls in this manner, the desired separating function and/or dosage-adjusting function can be exhibited in accordance with states such as shapes of the gas generating chambers.
Further, the present invention provides a gas generator comprising the retainer for a gas generator which is disposed in one or two or more gas generating chambers, wherein an outer side wall of the retainer is in contact with an inner side wall of the gas generating chamber, and a gas generating chamber is divided into at least two chambers in the longitudinal direction by means of closed end of the retainer.
The separation needs to be such that flame generated in one gas generating chamber isolated by the retainer may not transfer to the other. Such a separated state is referred as xe2x80x9ca flame-preventing statexe2x80x9d hereinafter. The retainer is disposed to separate the chambers in the xe2x80x9cflame-preventing statexe2x80x9d, and at the same time, it functions to retain a gas generating agent and/or to adjust an amount of the gas generating agents.
Further, the present invention provides a gas generator having the retainer for a gas generator disposed in one or two or more gas generating chambers, wherein the retainer is disposed to retain the gas generating agent and/or to adjust an amount of the gas generating agents, an outer side wall of the retainer is in contact with an inner side wall of the gas generating chamber, and a volume of the gas generating chamber is controlled by the closed end of the retainer.
In the present invention, the retainer is disposed in order to retain the gas generating agent and/or to adjust the dosage, and by appropriately moving and disposing the retainer in the longitudinal direction to adjust the volume of the gas generator, the above functions can be obtained.
In the above gas generator, at least two retainers for a gas generator can be disposed so that the open ends thereof may be arranged in the same direction.
The present invention provides a retainer for a gas generator disposed in the gas generator having one or two or more gas generating chambers, wherein the retainer is a combination of a larger-diameter cylinder having one end closed and the other end open and a smaller-diameter cylinder being integrated with the larger-diameter cylinder to project toward the inside as well as the open end of the larger-diameter cylinder.
In the retainer for a gas generator, a side-wall lengths of the larger-diameter cylinder and the smaller-diameter cylinder may be the same as or different from each other. Or in the retainer for a gas generator, a side-wall length of the larger-diameter cylinder may be longer or shorter than a side wall length of the smaller-diameter cylinder. By appropriately adjusting the side wall lengths of the larger-diameter cylinder and the smaller-diameter cylinder in the above-described manner, the desired separating function and/or dosage-adjusting function can be exhibited in accordance with states such as shapes of the gas generating chambers.
Further, the present invention provides a gas generator in which the retainer for a gas generator is disposed and one or two or more gas generating chambers are provided around a charge-transferring chamber, wherein the retainer is fitted into the charge-transferring chamber at the open end of the smaller-diameter cylinder, an outer side wall of the larger-diameter cylinder of the retainer is in contact with an inner side wall of the gas generating chamber, an inner side wall of the smaller-diameter cylinder is in contact with an outer side wall of the charge-transferring chamber, and a gas generating chamber is divided into at least two chambers in the longitudinal direction by the closed end in the flame-preventing state.
Further, the present invention provides a gas generator in which the retainer for a gas generator is disposed and one or two or more gas generating chambers are provided around a charge-transferring chamber, wherein the retainer is disposed in order to retain the gas generating agent and/or for to adjust the dosage, the retainer is fitted into the charge-transferring chamber at an open end of the smaller-diameter cylinder, an outer side wall of the larger-diameter cylinder of the retainer is in contact with an inner side wall of the gas generating chamber, an inner side wall of the smaller-diameter cylinder is in contact with an outer side wall of the charge-transferring chamber, and a volume of the gas generating chamber is controlled.
In the above gas generator, at least two retainers can be disposed so that open ends thereof may be arranged in the same direction. The at least two retainers may have the same specifications (the same shape, size, material and the like), or different specifications. However, the retainers in the same specifications are preferable because production can be facilitated, producing time can be shortened, and assembling operation can be more efficient.
The present invention provides a hybrid inflator for an inflating type safety system for vehicles provided with an air bag, which comprises an inflator housing, a gas generator installed in the inflator housing, and an ignition means chamber provided with ignition means which is connected to the gas generator, wherein the gas generator is the above-described gas generator.
In the above hybrid inflator, when the gas generator includes a first gas generating chamber and a second gas generating chamber disposed in series and adjacently to each other, a retainer for separating the first and second gas generating chambers in the flame-preventing state can be disposed with an open end thereof facing the first gas generating chamber.
By disposing the retainer with an open end thereof facing the first gas generating chamber in the above manner, in other words, by disposing the retainer with a closed end thereof facing the second gas generating chamber, the retainer is deformed so as to push and broaden the side wall portion thereof outwardly when the open portion of the retainer receives a pressure caused by combustion of the first gas generating agent in the first gas generating chamber. Therefore, the flame-preventing states of the first and second gas generating chambers are maintained, and consequently, an erroneous actuation caused by combustion of the second gas generating due to combustion of the first gas generating agent is prevented.
The present invention also provides a multistage-inflating hybrid inflator for a safety system of a vehicle provided with an air bag, which comprises an inflator housing, a gas generator provided in the inflator housing and ignition means chamber provided with an ignition means which is connected with the gas generator, wherein the interior of the inflator housing is filled with a pressurized medium containing an inert gas, the gas generator has a first gas generating chamber and a second gas generating chamber, each including a gas generating means, and further the ignition means comprises two initiators fixed in one initiator collar.
The igniting means of the present invention can be formed in such a manner that an inner shape of initiator collar is previously formed into the same shape as an outer shape of each of the two initiators, and the two initiators are fitted into the initiator collar. With the ignition means having the two initiators fixed in the one initiator collar in the above manner, the initiator collar and the two initiators become a single member and thus, the process of mounting the igniting means to the inflator housing is facilitated.
Further, by fixing two initiators into one initiator collar with resin to form the igniting means of the single member, the assembling process of the igniting means and the mounting process of the igniting means to the inflator housing are facilitated. In the present invention, it is not necessary to correspond the inner shape of the initiator collar to the outer shape of two initiators.
In the hybrid inflator of the present invention, as will be described later, the gas generating means which are the first gas generating agent accommodated in the first gas generating chamber and the second gas generating agent accommodated in the second gas generating chamber, or the gas generating means which is the gas generating agent accommodated in a single gas generating chamber can be determined in relation with composition of the pressurized medium stored into the inflator housing.
When the pressurized medium has a composition comprising an inert gas such as oxygen, argon, and helium (nitrogen is also included in the inert gas in the present invention), the oxygen works so as to convert carbon monoxide and hydrogen generated due to the combustion of a gas generating agent as gas generating means into carbon dioxide and water vapor: argon works so as to promote the thermal expansion of the pressurized medium. It is preferable to contain helium in the pressurized medium since the leakage of the pressurized medium can be detected easily, and consequently distribution of imperfect products can be prevented. A charging pressure of the pressurized medium (=pressure inside the inflator housing) is preferably 10,000 to 70,000 kPa and more preferably, 30,000 to 60,000 kPa. The pressurized medium may or may not include oxygen, and when oxygen is included, it is preferable that the maximum amount is 30 mol %.
As the first gas generating agent accommodated in the first gas generating chamber and the second gas generating agent accommodated in the second gas generating chamber, a gun propellant can be used for example. As the gun propellant, a single-base gun propellant, a double-base gun propellant and a triple-base gun propellant can be used. In addition to these propellants, it is possible to use a gun propellant obtained by mixing a secondary explosive, a binder, a plasticizer, a stabilizer and the like, and molding the resultant mixture in a desired shape.
The secondary explosive may include hexahydrotrinitrotriazine (RDX), cyclotetramethylene tetranitramine (HMX), pentaerithritol tetranitrate (PETN), and triaminoguanidine nitrate (TAGN). For example, when a gas generating agent using RDX as a secondary explosive is burnt in an oxygen-absent atmosphere under a pressure of 20,670 kPa and at a combustion temperature of 3348 K, formed gas is of a combustion gas comprises 33 mol % of nitrogen, 25 mol % of carbon monoxide, 23 mol % of water vapor, 8 mol % of carbon dioxide and other gas components.
The bonding agent may include cellulose acetate, cellulose acetate butylate, cellulose acetate propiolate, ethyl cellulose, polyvinyl acetate, azide polymer, polybutadiene, hydrogenated polybutadiene, and polyurethane; the plasticizer may comprise trimethylolethane trinitrate, butantriol trinitrate, nitroglycerine, bis (2,2-dinitropropyl) acetal/formal, glycidyl azide, and acetyltriethyl citrate and the like; and the stabilizer may comprise ethlcentralite, diphenylamine, and resocinol.
In a preferable ratio of the secondary explosive to the binder, plasticizer and stabilizer, secondary explosive is about 50 to 90 wt. % and the binder, plasticizer and stabilizer in all are about 10 to 50 wt. %.
It is difficult in some cases to burn the gas generating agent of the above-described composition under normal pressure. However, in the hybrid inflator according to the present invention, the interior thereof is maintained at a high pressure in advance, the gas generating agents can be burnt stably and smoothly.
In addition, as the first gas generating agent accommodated in the first gas generating chamber and the second gas generating agent accommodated in the second gas generating chamber, for example, it is possible to use a material including fuel and oxidizing agent, or fuel, oxidizing agent and slag-forming agent, being mixed with binder if required, and formed into a desired shape. If such a gas generating agent is used, a gas generated by combustion of the agent can be used for developing the air bag together with the pressurized medium. Especially when the gas generating agent including the slag-forming agent is used, an amount of mist discharged from the inflator can be largely reduced.
Preferably, the fuel can be one or two or more selected from guanidine derivative such as nitroguanidine (NQ) guanidine nitrite (GN), guanidine carbonate, amino nitroguanidine, amino guanidine nitrite, amino guanidine carbonate, diamino guanidine nitrite, diamino guanidine carbonate, and triamino guanidine nitrite. As the fuel, one or two or more materials selected from a group comprising tetrazole and tetrazole derivative can be used.
As the oxidizing agent, one or more materials selected from a group comprising strontium nitrate, potassium nitrate, ammonium nitrate, potassium perchlorate, copper oxide, ferrous oxide, a basic copper nitrate are preferably used. A preferable amount of the oxidizing agent is 10 to 80 parts by weight, and more preferably, 20 to 50 parts by weight with respect to 100 parts by weight of the fuel.
As the slag-forming agent, one or more materials selected from a group comprising acid clay, talc, bentonite, diatomaceous earth, kaolin, silica, alumina, sodium silicate, silicon nitride, silicon carbide, hydrotalsite, and a mixture thereof are preferably used. A preferable amount of the slag-forming agent is 0 to 50 parts by weight, and more preferably, 1 to 10 parts by weight with respect to 100 parts by weight of the fuel.
As the bonding agent, one or more materials selected from a group comprising sodium salt of sodium carboxymethylcellulose, hydroxyethyl cellulose, starch, polyvinyl alcohol, guar gum, microcrystal cellulose, polyacrylamide, and calcium stearate are preferably used. A preferable amount of binder is 0 to 30 parts by weight, and more preferably, 3 to 10 parts by weight with respect to 100 parts by weight of the fuel.
The present invention further provides an air bag system comprising an activation signal-outputting means including an impact sensor and a control unit, and a module case in which the above-described multistage-inflating hybrid inflator and an air bag are accommodated, wherein an inflating rate of the air bag can be controlled.
In the present invention, the term xe2x80x9ca gas generatorxe2x80x9d means a unit having a gas generating function of generating a high temperature combustion gas due to combustion of the gas generating means (gas generating agent) stored in the gas generator housing (gas generating chamber), thereby allowing the high temperature combustion gas to flow into the inflator housing. The hybrid inflator includes the gas generator inside an inflator housing thereof.
The above-described structures and functions can be combined with one another to practice the present invention.
Since the hybrid inflator of the present invention includes the two gas generating chambers, it is possible to inflate and develop the air bag smoothly and reliably, thereby enhancing safety. Further, since the interior is maintained at a high pressure, combustion of the gas generating agent is stabilized. Even when two gas generating chambers are provided, an increase in volume and weight of the hybrid inflator can be minimized by adjusting the arrangement of the two gas generating chambers.
The hybrid inflator comprising the gas generator which uses the retainer for a gas generator of the present invention eliminates a possibility of erroneous actuation, and the reliability of the product can be enhanced.